The present invention relates to a surgical implant that comprises a biodegradable polymer and a ceramic that is visible to radioscopy.
In surgery, it is known to use at least partly bioabsorbable, elongated, typically tubular, screw-like, thread-like or wire-like surgical implants and devices to support or connect or separate elongated organs, tissues, connective tissues, or their parts from each other. These objects include the skeletal system, various ducts, the intestines, blood vessels, tubes, such as the bronchi, the urinary tracts, the nerves, etc.
In this context, bioabsorbable material refers to a material made of a polymer, copolymer, or a polymer blend whose degradation and/or dissolution in an organism takes place by means of metabolic reactions and/or secretion through the kidneys, lungs, or through the intestines or the skin.
A number of publications describe various tubular screw-like, thread- or wire-like implants and surgical devices to be made of biologically stable or bioabsorbable materials. Implants and devices of this kind are disclosed e.g. in the publications U.S. Pat. Nos. 3,108,357; 3,155,095; 3,272,204; 3,463,158; 3,620,218; WO 83/03752; WO 84/03035; Daniel and Olding, Plast. Rec. Surg. 74 (1984) 329; WO 90/04982; Van Andersdahl et al., Seminars in Urology, Vol. 11 (1984) 180; Raja Subra Manian, ASAI Journal 40 (1994) M584; U.S. Pat. Nos. 4,768,507; 4,923,470; 4,973,301; 4,990,131; 4,994,066; 5,019,090; EPO 606 165 A1, WO 94/15583; U.S. Pat. Nos. 4,950,258; 5,160,341; and 4,085,629; 4,743,257.
Known implants and surgical devices of the above-mentioned or similar type, which are biostable or practically undegradable in tissues, have several disadvantages. Their biostable parts, such as fibers, plastic or metal threadings or rings or tubes or the like, remain in the body even after the organ or tissue has healed, and therefore implants and devices of this kind can later be detrimental to the patient, causing e.g. infections, inflammatory reactions, foreign body reactions, and/or they can release particles or corrosion products or the like, which may further cause harmful reactions in the body.
Many known bioabsorbable implants and surgical devices, e.g. many of those described in the above-mentioned publications as well as those of a corresponding type, do not cause the same kind of long-term complications as biostable implants and surgical devices do, because biodegradable implants and devices are dissolved and degraded biologically in the body, finally leaving the tissues entirely.
A defect with known bioabsorbable implants, however, has been the lack of an effective imaging method. This defect causes problems particularly when there is a need to determine the location of an implant or a device during and after its installation. If visual contact with the area is prevented, the installation can be considerably facilitated with an imaging method, with which the proceeding and installation in its place can be monitored during the operation. These imaging methods may include e.g. radiography, ultrasound, magnetography, computer tomography, gamma radiography, spectroscopy, or the like. It is also very important that the implant stays in its place in the installation object, and with a good imaging method, the position of the implant can be easily determined without surgical measures, such as endoscopy.
Bioabsorbable polymers, however, are poorly or not at all visible with imaging methods presently in use. In the present invention, it was surprisingly found that when a ceramic powder or the like is mixed with an implant or corresponding surgical device made of a bioabsorbable polymer, the implant or device can be made visible by imaging methods used in medicine, utilizing x-rays.
When different amounts of ceramic powder or the like, or combinations thereof, are mixed with an implant or a corresponding surgical device made of a bioabsorbable polymer, the implant or device can, depending on the surrounding tissue, be distinguished sufficiently well with an imaging method. Examples of imaging methods are x-ray, ultrasound, magnetography, computer tomography, gamma radiography, spectroscopy, or the like.
Implants or corresponding surgical devices according to the invention can be made of various bioabsorbable polymers, copolymers, or polymer blends, which have been described in a number of publications, for example in: Vainionpxc3xa4xc3xa4 et al., Prog. Polym. Sci. Vol.14, pp. 697-716 (1989); U.S. Pat. No. 4,700,704 (Jamiolkows and Shalaby); U.S. Pat. No. 4,653,497 (Bezwada, Shalaby and Newman); U.S. Pat. No. 4,649,921 (Koelmel, Jamiolkows and Bezwada); U.S. Pat. No. 4,559,945 (Koelmel and Shalaby); U.S. Pat. No. 4,532,928 (Rezada, Shalaby and Jamiolkows); U.S. Pat. No. 4,605,730 (Shalaby and Jamiolkows); U.S. Pat. No. 4,441,496 (Shalaby and Koelmel); U.S. Pat. No. 4,435,590 (Shalaby and Jamiolkows).
The implants or corresponding surgical devices according to the invention can have a structure which is not reinforced, such as made with melt processing techniques or with solution techniques, or they can be reinforced by using e.g. self-reinforcing or reinforcing with absorbable polymer or ceramic fibers.
The method for manufacturing an implant or a corresponding surgical device according to the invention is based on the fact that ceramic powder or the like is added to the material of the implant or corresponding surgical device to make the implant or corresponding surgical device visible with different imaging methods. Examples of the imaging methods are x-ray, ultrasound, magnetography, computer tomography, gamma radiography, spectroscopy, or the like.
In an advantageous embodiment, the implant or corresponding surgical device is manufactured in a way that the quantity of the ceramic powder or the like, added into the polymer, is different in different parts of the implant or corresponding surgical device. For example, the quantity of the ceramic powder or the like can be greater at the first end than at the second end of the implant or corresponding surgical device. Thus, by this method, the visibility of the implant or corresponding surgical device by the imaging method can be made different at different ends of the implant.
The content of the ceramic powder or the like can gradually decrease in the direction of the longitudinal axis of the implant or corresponding surgical device, or the content of the ceramic powder or the like may be different in the body part as compared with the protruding parts of the implant or corresponding surgical device. Further, ceramic powder or the like can be present only in a certain part or location of the implant or corresponding surgical device in a way that there is no ceramic powder or the like in the other parts of the implant or corresponding surgical device at all. By this method, it is possible to manufacture implants or corresponding surgical devices whose visibility with an imaging method is different in different parts of the implant.
The quantity of the ceramic powder or the like can decrease gradually in the direction of the transverse axis of the implant. In this way it is possible to manufacture implants or corresponding surgical devices whose visibility with imaging methods is different in the central part than in the outer shell of the piece.
The invention will become apparent from the following description, with reference to the appended figures and drawings presenting some examples on implants or corresponding surgical devices according to the invention, as well as on applications on methods for their manufacture.